Modern garages have a capacity for two, three or more cars. In a two-car garage, a single door is often used. Commonly such doors are of the overhead type opened and closed by an electrically powered door operator. However, single doors used for two or more garage bays are wide, unstable, tend to drag on one side and can cock and jam. Also, the weight of such large doors requires additional motor power to drive them open and closed. It has been found preferable, therefore, to use a separate door for each garage bay to insure reliable operation and afford privacy, security and less power usage. Smaller and lighter overhead doors also minimize mechanical problems with the door mounting mechanisms.
Non-residential garages and the like often include a number of bays that desirably can be opened individually or in unison. For example, during warm weather, receiving and shipping bays are normally opened all day, thus being opened and closed together at the beginning and end of the work period. On the other hand, during cold weather, the bays are opened individually. In another example, a firehouse normally opens one door to dispatch a single piece of equipment, but for major fires all doors must be opened together.
A plurality of overhead doors for multiple bay garages and the like, while providing many advantages, are relatively expensive when electrically operated by conventional means. Each door must be driven by a separate power unit which normally includes a motor, speed reducer and controls. With a three bay garage, for example, three separate motor power units drive the three doors. The power units are activated by manual switches and, quite commonly, radio control units responding to signals generated by small radio transmitters. The redundant separate motor power units for each of the three doors involves a substantial expense for this type of installation.